The Preclinical Therapeutics Core (Core) provides in vivo services to UCSF Helen Diller Family Comprehensive Cancer Center (Center) investigators. Offering a variety of tumor engraftment-based cancer models for use in preclinical oncology trials, the Core provides a complete set of services that include consultation regarding experimental design, tumor cell culture and implantation in mice, administration of experimental agents, monitoring of tumor burden and response to therapy, and interpretation of study results. The Core maintains a cryorepository of commonly used human cancer cell lines derived from multiple tumor types along with data regarding their in vivo growth characteristics, as well as a collection of patient-derived tumor xenograft models. The Core's offerings also include pharmacological analysis and optimization of novel agents such as compound formulation, pharmacokinetics (PK), pharmacodynamics (PD), and safety-toxicity analyses. The Core is also a resource of expertise in small animal survival surgery, and is available to provide training in these techniques on a recharge basis. Although the Core primarily functions to test experimental anti-cancer agents in vivo, it also provides animal models of human cancer for use in novel diagnostic, tumor imaging, and basic mechanistic research. The Core oversees, maintains, and provides as a service a number of small animal imaging technologies housed within the barrier facility. The availability of centralized cell and animal resources, together with personnel with expertise in conducting preclinical studies, ensures appropriate experimental design and reproducibility, compliance with local and federal regulatory guidelines for tumor-bearing animals, and maximum resource utilization through coordinated animal purchasing and housing.